The invention concerns a rolling assembly consisting of a tire and a wheel, the wheel comprising at least one collar that ensures connection between a substantially cylindrical wheel rim and the tire.
Most known tire-wheel assemblies are so constructed that the wheel can be taken off the vehicle to which it is fitted, the tire then being removed from the wheel by a workshop operation using appropriate machinery. A usual wheel comprises inter alia a rim which, depending on the vehicle and the assembly considered, may be made in one or more parts. The fitting of a tire, which consists in positioning the tire beads correctly on the seats and against the flanges of a rim, is not an easy operation even for a specialist and all the more so for a normal user, and does not always lead to the expected results: correct position, perfect airtightness, sufficient grip against the seat, etc. The same applies to the removal of the tire, which requires effort and care beyond the ability of the average driver. To simplify the operations of fitting and removing a tire, that is to say, to obviate the need for special machinery and considerable knowledge, a method has been proposed which consists in fitting the tire onto a cylindrical or substantially cylindrical support, a support which will be referred to by extension of the term as the rim, simply by virtue of a transverse relative movement between the rim and the tire. Clearly, the implementation of the method requires a third element.
For civil engineering equipment, patent FR 2 087 770 describes beads provided on their bearing surfaces with one or more annular metallic components fixed permanently on the beads, the components acting as wheel rim seats and being designed to rest on a cylindrical support attached to the vehicle being equipped and playing the part of a rim base or rim. The above third element is then the assembly of the metallic components that make it possible to slide the try-seat assembly onto the support, so ensuring easier fitting and removal.
For smaller tires with the usual structures, i.e. ones with at least one carcass reinforcement and a tread connected to two beads by two sidewalls, patent FR 2 773 745 describes an assembly comprising the said tire, a substantially cylindrical support or rim and a third element consisting of a collar or adaptor specifically developed to be associated with the tire and to constitute a sub-assembly having the desired fitting and removal properties. The collar, whose axial width is essentially equal to the width of the support or rim, is intended to be fitted under the beads of the tire of ordinary structure and comprises two seats to receive the beads. Together with the tire it forms a closed torus that defines an airtight tire chamber, and constitutes the radially inside wall of the torus. It comprises a blocking means to immobilize the tire axially on the rim; the said means are formed on the radially inside face, are designed to co-operate with a complementary element formed on the rim to oppose any axial movement between the rim and tire, and are formed in a part of the collar that shows a certain degree of flexibility between a natural, free position and a position stressed radially outwards in which the blocking means are free from any engagement with the complementary element. When the airtight chamber is at the same pressure as the atmospheric pressure, the blocking means are engaged with the complementary element so as to lock the tire axially, and can only be released by the imposition of external means. According to the invention described, the operations of fitting and removal entail that the pressure in the chamber formed by the tire and the collar is reduced, this underpressure causing most of the collar to increase in diameter and therefore allowing the tire to fit easily onto the rim, the tire then being immobilized by engagement of the blocking means once the pressure has been restored. During removal, the production of an underpressure in the airtight chamber allows the blocking means to increase their diameter so that the tire can slide off the rim. In a general sense the blocking means advantageously consist of a protuberance or groove on the collar associated with a matching groove or protuberance on the rim. By an appropriate choice of the materials, design and dimensions of the collar, it is very easily possible to confer on most of the axial portion of the said collar the flexibility required for the deformations desired.
A collar made from a reinforced elastomeric material, having on each side of its equatorial plane an edge designed to receive a tire bead, the edge being reinforced mainly by a metallic spring, and having between the two edges thereof a central part comprising the blocking means and reinforced by a ply of radial reinforcement elements has the following disadvantages when the dimensional variations of tire beads are taken into account: the occurrence of excessive friction of the edges of the collar against the rim during fitting, and the occurrence of not inconsiderable slippage between the radially inside face of the collar and the radially upper face of the rim during the use of the rolling system, which lead to unacceptable wear of the collar and the rim and to excessive deformation of the radial reinforcement elements, this deformation being harmful in relation to the desired endurance.